Clinical impact of pulmonary sampling site in the diagnosis of ventilator-associated pneumonia: A prospective study using bronchoscopic bronchoalveolar lavage

Purpose It is unclear whether ventilator-associated pneumonia (VAP) is actually a bilateral and multifocal process. In addition, the diagnostic role of chest x-ray is under debate. Assuming a low microbiologic concordance between the left and right lungs, the reliability of a single pulmonary sampling becomes questionable. The purpose of this study was to determine whether the choice of the pulmonary sampling area is clinically relevant in the management of VAP. Methods In 79 patients admitted to a university general intensive care unit with clinically suspected VAP, right- and left-lung bronchoalveolar lavage (BAL) samples were taken with separate bronchoscopes and quantitatively cultured. Primary end-point variable was microbiologic concordance rate between right- and left-lung BAL cultures. Secondary outcomes included predictors of microbiologic concordance, rates of appropriate antibiotic treatment, and diagnostic accuracy of chest x-ray. Results BAL cultures were bilaterally negative in 21 (27%) of 79 patients, bilaterally positive in 36 (46%), and unilaterally positive (right in 12, left in 10) in 22 (28%). Intra-patient concordance was observed in 47 (59.5%) of 79 cases and independently associated with purulent secretions and bilateral infiltrates on chest x-ray. In simulated prescribing experiments, treatments chosen based on right or left cultures alone were as appropriate as those based on bilateral data in >90% of cases. The presence of a radiographic infiltrate in the sampling area predicted BAL culture positivity with a positive predictive value of only 61%. Conclusions In patients with clinically suspected VAP (especially those without purulent secretions or without radiographically documented bilateral infiltrates), quantitative culture of a single BAL sample may provide an incomplete assessment of lung microbiology, without having a relevant impact on the appropriateness of antimicrobial treatment. These findings suggest that single sampling of respiratory secretions, regardless radiographic opacity, seems to be a reliable diagnostic method in the management of VAP.